The Fertilizer-Effect on Al, Ba, Fe, Mn and Ni Released in a Watershed with Influence of Sugar Cane Crops in the Sao Paulo State, Brazil

摘要

Sao Paulo State is the main sugar cane producer and these agricultural activities are carried out in predominantly sandy soils, which require large amounts of phosphate fertilizers and amendments. This work evaluated the fertilizer-effect on the Al, Ba, Fe, Mn and Ni released in a watershed with influence of sugar cane crops in the Sao Paulo State, Brazil, namely the Monjolo Grande Stream basin. Five surface water sampling campaigns were carried out at the mouth of Monjolo Grande Stream in February, April, June, September and November 2010, characterizing the following parameters: discharge, pH, temperature, electric conductivity, dissolved oxygen and total and dissolved concentrations of Al, Ba, Fe, Mn and Ni. Approximately 99% of Al and Fe are transported annually in association with suspended sediments carried to the Monjolo Grande Stream by sheet erosion. The results also demonstrated that the increasing Al, Ba, Fe and Mn concentrations dissolved in the waters of the Monjolo Grande Stream basin in the wet season are associated to phosphate fertilizers and amendments that are used extensively in agrichemical activities. However, with the current application rates, there has been no increase in the dissolved concentrations of these metals at levels that could pose risks to human health.